Gas turbine engines (GTEs) produce power by extracting energy from a flow of hot gas produced by combustion of fuel in a stream of compressed air. In general, turbine engines have an upstream air compressor coupled to a downstream turbine with a combustion chamber (“combustor”) in between. Energy is released when a mixture of compressed air and fuel is burned in the combustor. In a typical turbine engine, one or more fuel injectors direct a liquid or gaseous hydrocarbon fuel into the combustor for combustion. The resulting hot gases are directed over blades of the turbine to spin the turbine and produce mechanical power. The engine efficiency can be increased by passing a higher temperature gas into the turbine. However, material properties and cooling limitations limit the turbine inlet temperature.
High performance GTEs include cooling passages and cooling fluid to improve reliability and cycle life of individual components within the GTE. For example, in cooling the turbine section, cooling passages are provided within the turbine blades to direct a cooling fluid therethrough. Conventionally, a portion of the compressed air is bled from the air compressor to cool components such as the turbine blades. The amount of air bled from the air compressor, however, is limited so that a sufficient amount of compressed air is available for engine combustion to perform useful work.
U.S. Pat. No. 8,585,351 to Bregman et al. (the '351 patent) describes a gas turbine blade having a cooling air channel extending from an air inlet opening in the root throughout the airfoil to a plurality of air outlets at the pressure side and the leading edge of the top of the tip of the airfoil. The concentration of air outlets at the top of the tip of the airfoil is higher on the pressure side than on the suction side. The '351 patent also discloses a cooling arrangement with at least two air channel systems. According to the '351 patent, the difference in concentration of air outlets in different regions of the blade, and the use of two air channel systems results in the cooling fluid being lead more precisely to the parts of the tip where the most heat is generated during operation of the blade. However, centrifugal forces and air flow at boundary layers may still prevent some areas of the turbine blade from being adequately cooled.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.